The overall objectives of this project are to identify biochemical effects of hormones on tissues of the reproductive system (endometrium, testis), with emphasis on the effects of progesterone and synthetic progestins on steroid receptor levels and on enzymatic activities in these tissues. Experiments to be conducted on specimens of human endometrium and on endometrial cells in culture aim to obtain further evidence for the existence of different types of binding sites of estrogen-receptor complexes on endometrial chromatin, possibly associated with different biologic actions. Hormonal regulation of enzymatic activities and steroid receptor levels will also be investigated in these preparations. Effects of the administration of progestins and gonadotropins on testicular enzymes and receptors will be studied in adult rats. These investigations attempt to provide evidence of direct actions of progestins on the testis.